This invention relates in general to energy conversion systems and, more particularly, to an air motor system for driving small recreational boats.
Manually-powered small boats have long been used for transportation and recreation. Many such boats are powered by oars, paddles or the like. These like methods are not convenient for the occasional recreational user, since they require considerable skill and a high, constant work output. Later, "paddle boats" were developed using large side or rear-mounted paddle wheels driven by the operators hands or feet through mechanical crank systems. Direct manual drive of a propeller was also attempted, as described by Willis in U.S. Pat. No. 636,479. While these require less skill to operate, they are still energy-inefficient and require a constant input of manual energy to keep the boat in motion.
A number of air drive systems have been developed in order to reduce the need for constant word and to improve systems inefficiency. These systems use a manual air compression systems, such as hand or foot driven piston-type air pumps, a tank to accumulate the pressurized air into rotary motion at an underwater propeller. These permit the operator to build up pressure, then rest while the propeller continues to operate on stored energy for a period.
Typical of these prior air drive systems are those described by Crowe in U.S. Pat. No. 808,346 and Smith in U.S. Pat. No. 453,217. While these early air drive mechanisms are apparently workable, they are mechanically complex, heavy and inefficient, particularly in using turbines to convert air pressure to rotary motion. Turbines tend to be very inefficient at the low rotational speeds involved in such boats.
Other manual boat drives include directly coupled manual pump means driving a water jet as described by Ch'iu in U.S. Pat. No. 3,487,806 and the direct pedal operated fluid drive described by Sever et al in U.S. Pat. No. 2,720,185. Again, these have disadvantages in requiring constant effort to keep the boat in motion and inefficient energy conversion.
Thus, there is a continuing need for energy efficient, compact and lightweight manual drive systems for small recreational boats which allow the accumulation of energy to permit the operator to rest for periods while continuing to operate the boat and in particular for improved air motors suitable for use in such systems.